Health survey dilemma: Can you hear me now?

Many telephone surveillance systems -- including the world's largest, the Behavioral Risk Factor Surveillance System, which was established in 1984 by the Centers for Disease Control and Prevention and state health departments -- traditionally have collected data by landline phones. Now, sizeable chunks of the population have chosen to become entirely wireless, making it much more difficult -- and expensive -- to reach them. The National Health Interview Survey found that half of cell-phone-only users are younger than 30 and 22% are low-income adults, or those earning less than 200% of the poverty level. In addition, the cell-phone-only users were: The major issue is how representative cell phone users are of the entire population, and how to maintain accurate surveys.